AAVSO Sudden Ionospheric Disturbance Report May 1991 Observers: A-01 A-03 A-09 A-19 A-40 A-50 A-52 A-59 A-61 A-62 A-63 A-64 A-65 A-66 A-67 A-68 A-69 A-70 A-71 A-72 YYMMDD Event Peak (UT) Importance 910501 0020 2+ 910501 0951 1- 910501 1146 1+ 910501 1747 2 910501 1821 1+ 910501 1948 1+ 910501 2030 1 910502 1045 1 910503 1838 2+ 910503 2236 2+ 910504 0604 1 910504 0627 1 910504 1401 1- 910504 1601 1+ 910504 2234 1 910504 2316 1- 910505 0421 1 910505 0530 1 910505 0600 2 910505 1015 1- 910505 1045 1- 910505 1225 1+ 910505 1515 1- 910505 2001 1- 910505 2033 1- 910505 2045 1- 910505 2058 2+ 910505 2216 1 910506 0600 1+ 910506 1700 2+ 910506 1946 1- 910506 2127 1+ 910506 2152 1 910506 2330 2 910507 0006 1+ 910507 0031 3 910507 0741 2+ 910507 1007 1 910507 1039 2+ 910507 1448 2 910507 1530 1 910507 1805 2 910507 1945 2 910507 2242 1 910508 0108 1 910508 0144 2 910508 1601 2+ 910508 1840 2+ 910508 2007 1- 910508 2016 2 910508 2145 1- 910508 2301 2+ 910509 0844 1+ 910509 0910 1+ 910509 1054 2+ 910509 1132 1- 910509 1149 1- 910509 1214 1+ 910509 1240 1+ 910509 1509 1 910509 1730 1 910509 1750 2+ 910509 2023 1- 910510 1915 2 910510 1946 2+ 910510 2007 1+ 910510 2345 2 910511 0053 1- 910511 0516 1- 910511 0642 1+ 910511 0812 2+ 910511 1135 2+ 910511 1322 2+ 910511 1421 2 910511 1521 2+ 910511 1614 1 910511 1644 1+ 910511 1830 1- 910511 2015 3+ 910512 0600 2+ 910512 0721 1+ 910512 0805 2 910512 1033 3 910512 1233 2 910512 1321 2 910512 1614 2+ 910512 1717 1 910512 1736 2+ 910512 2016 1+ 910512 2237 1+ 910512 2300 1- 910513 0039 1+ 910513 0121 3 910513 0514 2+ 910513 2130 1+ 910514 0723 1- 910514 1131 2 910514 1739 2 910515 1103 1- 910515 1451 1 910515 1908 2+ 910515 2044 2+ 910516 0649 3+ 910516 1444 1+ 910517 0906 2+ 910517 1344 2+ 910517 1353 1- 910517 1712 1 910517 1828 1 910517 2108 1- 910517 2222 2+ 910517 2306 1 910518 0445 1 910518 0502 3+ 910518 1534 1+ 910518 1613 1+ 910518 1646 1+ 910518 1915 1- 910518 1932 1- 910518 2054 1 910518 2116 1- 910519 1354 3+ 910521 1651 1- 910522 0007 1 910522 0550 2+ 910522 0643 2 910523 0137 1+ 910524 1845 1 910525 1415 2 910525 1512 1- 910525 2143 2 910525 2215 1- 910525 2229 2 910526 0853 2 910526 2030 1- 910527 0144 2 910527 1310 1 910527 1522 2 910527 1600 1- 910527 1809 1+ 910527 1906 2+ 910527 1955 1 910527 2015 2+ 910527 2101 1 910527 2222 1 910527 2313 2 910528 0123 2 910528 0712 1- 910528 0729 2 910528 0754 1- 910528 1021 2 910528 1215 1- 910528 1225 1 910528 1313 2+ 910528 1444 1- 910528 1517 1- 910528 1623 2+ 910528 1833 1+ 910528 2014 2+ 910528 2117 2+ 910528 2200 1- 910528 2213 2+ 910529 0027 1+ 910529 0121 1+ 910529 0301 2 910529 0448 2 910529 0717 2 910529 1208 2+ 910529 1400 1- 910529 1426 2 910529 1533 3 910529 1633 2+ 910529 1954 2+ 910529 2344 2+ 910530 0716 2+ 910530 0940 2+ 910530 1128 2+ 910530 1413 2+ 910530 1747 1+ 910530 2208 1+ 910530 2300 2 910531 0247 1+ 910531 0410 2+ 910531 0840 2+ 910531 1234 1 910531 1432 1+ 910531 1656 2+ ******************************************* Importance Summary May 1991 1- events: 38 1 events: 31 1+ events: 33 2 events: 32 2+ events: 45 3 events: 4 3+ events: 4 Total events: 187